/**
 * @class Ext.dom.Element
 */
Ext.dom.Element.override((function() {

    var doc = document,
        win = window,
        alignRe = /^([a-z]+)-([a-z]+)(\?)?$/,
        round = Math.round;

    return {

        /**
         * Gets the x,y coordinates specified by the anchor position on the element.
         * @param {String} [anchor='c'] The specified anchor position.  See {@link #alignTo}
         * for details on supported anchor positions.
         * @param {Boolean} [local] True to get the local (element top/left-relative) anchor position instead
         * of page coordinates
         * @param {Object} [size] An object containing the size to use for calculating anchor position
         * {width: (target width), height: (target height)} (defaults to the element's current size)
         * @return {Number[]} [x, y] An array containing the element's x and y coordinates
         */
        getAnchorXY: function(anchor, local, mySize) {
            //Passing a different size is useful for pre-calculating anchors,
            //especially for anchored animations that change the el size.
            anchor = (anchor || "tl").toLowerCase();
            mySize = mySize || {};

            var me = this,
                isViewport = me.dom == doc.body || me.dom == doc,
                myWidth = mySize.width || isViewport ? Ext.dom.Element.getViewWidth() : me.getWidth(),
                myHeight = mySize.height || isViewport ? Ext.dom.Element.getViewHeight() : me.getHeight(),
                xy,
                myPos = me.getXY(),
                scroll = me.getScroll(),
                extraX = isViewport ? scroll.left : !local ? myPos[0] : 0,
                extraY = isViewport ? scroll.top : !local ? myPos[1] : 0;

            // Calculate anchor position.
            // Test most common cases for picker alignment first.
            switch (anchor) {
                case 'tl' : xy = [ 0,                    0];
                            break;
                case 'bl' : xy = [ 0,                    myHeight];
                            break;
                case 'tr' : xy = [ myWidth,              0];
                            break;
                case 'c'  : xy = [ round(myWidth * 0.5), round(myHeight * 0.5)];
                            break;
                case 't'  : xy = [ round(myWidth * 0.5), 0];
                            break;
                case 'l'  : xy = [ 0,                    round(myHeight * 0.5)];
                            break;
                case 'r'  : xy = [ myWidth,              round(myHeight * 0.5)];
                            break;
                case 'b'  : xy = [ round(myWidth * 0.5), myHeight];
                            break;
                case 'br' : xy = [ myWidth,              myHeight];
            }
            return [xy[0] + extraX, xy[1] + extraY];
        },

        /**
         * Gets the x,y coordinates to align this element with another element. See {@link #alignTo} for more info on the
         * supported position values.
         * @param {String/HTMLElement/Ext.Element} element The element to align to.
         * @param {String} [position="tl-bl?"] The position to align to (defaults to )
         * @param {Number[]} [offsets] Offset the positioning by [x, y]
         * @return {Number[]} [x, y]
         */
        getAlignToXY : function(alignToEl, posSpec, offset) {
            alignToEl = Ext.get(alignToEl);

            if (!alignToEl || !alignToEl.dom) {
                //<debug>
                Ext.Error.raise({
                    sourceClass: 'Ext.dom.Element',
                    sourceMethod: 'getAlignToXY',
                    msg: 'Attempted to align an element that doesn\'t exist'
                });
                //</debug>
            }

            offset = offset || [0,0];
            posSpec = (!posSpec || posSpec == "?" ? "tl-bl?" : (!(/-/).test(posSpec) && posSpec !== "" ? "tl-" + posSpec : posSpec || "tl-bl")).toLowerCase();

            var me = this,
                    myPosition,
                    alignToElPosition,
                    x,
                    y,
                    myWidth,
                    myHeight,
                    alignToElRegion,
                    viewportWidth = Ext.dom.Element.getViewWidth() - 10, // 10px of margin for ie
                    viewportHeight = Ext.dom.Element.getViewHeight() - 10, // 10px of margin for ie
                    p1y,
                    p1x,
                    p2y,
                    p2x,
                    swapY,
                    swapX,
                    docElement = doc.documentElement,
                    docBody = doc.body,
                    scrollX = (docElement.scrollLeft || docBody.scrollLeft || 0),// + 5, WHY was 5 ever added?
                    scrollY = (docElement.scrollTop  || docBody.scrollTop  || 0),// + 5, It means align will fail if the alignTo el was at less than 5,5
                    constrain, //constrain to viewport
                    align1,
                    align2,
                    alignMatch = posSpec.match(alignRe);

            //<debug>
            if (!alignMatch) {
                Ext.Error.raise({
                    sourceClass: 'Ext.dom.Element',
                    sourceMethod: 'getAlignToXY',
                    el: alignToEl,
                    position: posSpec,
                    offset: offset,
                    msg: 'Attemmpted to align an element with an invalid position: "' + posSpec + '"'
                });
            }
            //</debug>

            align1 = alignMatch[1];
            align2 = alignMatch[2];
            constrain = !!alignMatch[3];

            //Subtract the aligned el's internal xy from the target's offset xy
            //plus custom offset to get this Element's new offset xy
            myPosition = me.getAnchorXY(align1, true);
            alignToElPosition = alignToEl.getAnchorXY(align2, false);

            x = alignToElPosition[0] - myPosition[0] + offset[0];
            y = alignToElPosition[1] - myPosition[1] + offset[1];

            // If position spec ended with a "?", then constrain to viewport is necessary
            if (constrain) {
                myWidth = me.getWidth();
                myHeight = me.getHeight();
                alignToElRegion = alignToEl.getRegion();
                //If we are at a viewport boundary and the aligned el is anchored on a target border that is
                //perpendicular to the vp border, allow the aligned el to slide on that border,
                //otherwise swap the aligned el to the opposite border of the target.
                p1y = align1.charAt(0);
                p1x = align1.charAt(align1.length - 1);
                p2y = align2.charAt(0);
                p2x = align2.charAt(align2.length - 1);
                swapY = ((p1y == "t" && p2y == "b") || (p1y == "b" && p2y == "t"));
                swapX = ((p1x == "r" && p2x == "l") || (p1x == "l" && p2x == "r"));

                if (x + myWidth > viewportWidth + scrollX) {
                    x = swapX ? alignToElRegion.left - myWidth : viewportWidth + scrollX - myWidth;
                }
                if (x < scrollX) {
                    x = swapX ? alignToElRegion.right : scrollX;
                }
                if (y + myHeight > viewportHeight + scrollY) {
                    y = swapY ? alignToElRegion.top - myHeight : viewportHeight + scrollY - myHeight;
                }
                if (y < scrollY) {
                    y = swapY ? alignToElRegion.bottom : scrollY;
                }
            }
            return [x,y];
        },


        /**
         * Anchors an element to another element and realigns it when the window is resized.
         * @param {String/HTMLElement/Ext.Element} element The element to align to.
         * @param {String} position The position to align to.
         * @param {Number[]} [offsets] Offset the positioning by [x, y]
         * @param {Boolean/Object} [animate] True for the default animation or a standard Element animation config object
         * @param {Boolean/Number} [monitorScroll] True to monitor body scroll and reposition. If this parameter
         * is a number, it is used as the buffer delay (defaults to 50ms).
         * @param {Function} [callback] The function to call after the animation finishes
         * @return {Ext.Element} this
         */
        anchorTo : function(el, alignment, offsets, animate, monitorScroll, callback) {
            var me = this,
                dom = me.dom,
                scroll = !Ext.isEmpty(monitorScroll),
                action = function() {
                    Ext.fly(dom).alignTo(el, alignment, offsets, animate);
                    Ext.callback(callback, Ext.fly(dom));
                },
                anchor = this.getAnchor();

            // previous listener anchor, remove it
            this.removeAnchor();
            Ext.apply(anchor, {
                fn: action,
                scroll: scroll
            });

            Ext.EventManager.onWindowResize(action, null);

            if (scroll) {
                Ext.EventManager.on(win, 'scroll', action, null,
                        {buffer: !isNaN(monitorScroll) ? monitorScroll : 50});
            }
            action.call(me); // align immediately
            return me;
        },

        /**
         * Remove any anchor to this element. See {@link #anchorTo}.
         * @return {Ext.dom.Element} this
         */
        removeAnchor : function() {
            var me = this,
                anchor = this.getAnchor();

            if (anchor && anchor.fn) {
                Ext.EventManager.removeResizeListener(anchor.fn);
                if (anchor.scroll) {
                    Ext.EventManager.un(win, 'scroll', anchor.fn);
                }
                delete anchor.fn;
            }
            return me;
        },

        getAlignVector: function(el, spec, offset) {
            var me = this,
                myPos = me.getXY(),
                alignedPos = me.getAlignToXY(el, spec, offset);

            el = Ext.get(el);
            //<debug>
            if (!el || !el.dom) {
                Ext.Error.raise({
                    sourceClass: 'Ext.dom.Element',
                    sourceMethod: 'getAlignVector',
                    msg: 'Attempted to align an element that doesn\'t exist'
                });
            }
            //</debug>

            alignedPos[0] -= myPos[0];
            alignedPos[1] -= myPos[1];
            return alignedPos;
        },

        /**
         * Aligns this element with another element relative to the specified anchor points. If the other element is the
         * document it aligns it to the viewport. The position parameter is optional, and can be specified in any one of
         * the following formats:
         *
         * - **Blank**: Defaults to aligning the element's top-left corner to the target's bottom-left corner ("tl-bl").
         * - **One anchor (deprecated)**: The passed anchor position is used as the target element's anchor point.
         *   The element being aligned will position its top-left corner (tl) to that point. *This method has been
         *   deprecated in favor of the newer two anchor syntax below*.
         * - **Two anchors**: If two values from the table below are passed separated by a dash, the first value is used as the
         *   element's anchor point, and the second value is used as the target's anchor point.
         *
         * In addition to the anchor points, the position parameter also supports the "?" character.  If "?" is passed at the end of
         * the position string, the element will attempt to align as specified, but the position will be adjusted to constrain to
         * the viewport if necessary.  Note that the element being aligned might be swapped to align to a different position than
         * that specified in order to enforce the viewport constraints.
         * Following are all of the supported anchor positions:
         *
         * <pre>
         * Value  Description
         * -----  -----------------------------
         * tl     The top left corner (default)
         * t      The center of the top edge
         * tr     The top right corner
         * l      The center of the left edge
         * c      In the center of the element
         * r      The center of the right edge
         * bl     The bottom left corner
         * b      The center of the bottom edge
         * br     The bottom right corner
         * </pre>
         *
         * Example Usage:
         *
         *     // align el to other-el using the default positioning ("tl-bl", non-constrained)
         *     el.alignTo("other-el");
         *
         *     // align the top left corner of el with the top right corner of other-el (constrained to viewport)
         *     el.alignTo("other-el", "tr?");
         *
         *     // align the bottom right corner of el with the center left edge of other-el
         *     el.alignTo("other-el", "br-l?");
         *
         *     // align the center of el with the bottom left corner of other-el and
         *     // adjust the x position by -6 pixels (and the y position by 0)
         *     el.alignTo("other-el", "c-bl", [-6, 0]);
         *
         * @param {String/HTMLElement/Ext.Element} element The element to align to.
         * @param {String} [position="tl-bl?"] The position to align to
         * @param {Number[]} [offsets] Offset the positioning by [x, y]
         * @param {Boolean/Object} [animate] true for the default animation or a standard Element animation config object
         * @return {Ext.Element} this
         */
        alignTo: function(element, position, offsets, animate) {
            var me = this;
            return me.setXY(me.getAlignToXY(element, position, offsets),
                    me.anim && !!animate ? me.anim(animate) : false);
        },

        /**
         * Returns the `[X, Y]` vector by which this element must be translated to make a best attempt
         * to constrain within the passed constraint. Returns `false` is this element does not need to be moved.
         *
         * Priority is given to constraining the top and left within the constraint.
         *
         * The constraint may either be an existing element into which this element is to be constrained, or
         * an {@link Ext.util.Region Region} into which this element is to be constrained.
         *
         * @param {Ext.Element/Ext.util.Region} constrainTo The Element or Region into which this element is to be constrained.
         * @param {Number[]} proposedPosition A proposed `[X, Y]` position to test for validity and to produce a vector for instead
         * of using this Element's current position;
         * @returns {Number[]/Boolean} **If** this element *needs* to be translated, an `[X, Y]`
         * vector by which this element must be translated. Otherwise, `false`.
         */
        getConstrainVector: function(constrainTo, proposedPosition) {
            if (!(constrainTo instanceof Ext.util.Region)) {
                constrainTo = Ext.get(constrainTo).getViewRegion();
            }
            var thisRegion = this.getRegion(),
                    vector = [0, 0],
                    shadowSize = this.shadow && this.shadow.offset,
                    overflowed = false;

            // Shift this region to occupy the proposed position
            if (proposedPosition) {
                thisRegion.translateBy(proposedPosition[0] - thisRegion.x, proposedPosition[1] - thisRegion.y);
            }

            // Reduce the constrain region to allow for shadow
            // TODO: Rewrite the Shadow class. When that's done, get the extra for each side from the Shadow.
            if (shadowSize) {
                constrainTo.adjust(0, -shadowSize, -shadowSize, shadowSize);
            }

            // Constrain the X coordinate by however much this Element overflows
            if (thisRegion.right > constrainTo.right) {
                overflowed = true;
                vector[0] = (constrainTo.right - thisRegion.right);    // overflowed the right
            }
            if (thisRegion.left + vector[0] < constrainTo.left) {
                overflowed = true;
                vector[0] = (constrainTo.left - thisRegion.left);      // overflowed the left
            }

            // Constrain the Y coordinate by however much this Element overflows
            if (thisRegion.bottom > constrainTo.bottom) {
                overflowed = true;
                vector[1] = (constrainTo.bottom - thisRegion.bottom);  // overflowed the bottom
            }
            if (thisRegion.top + vector[1] < constrainTo.top) {
                overflowed = true;
                vector[1] = (constrainTo.top - thisRegion.top);        // overflowed the top
            }
            return overflowed ? vector : false;
        },

        /**
        * Calculates the x, y to center this element on the screen
        * @return {Number[]} The x, y values [x, y]
        */
        getCenterXY : function(){
            return this.getAlignToXY(doc, 'c-c');
        },

        /**
        * Centers the Element in either the viewport, or another Element.
        * @param {String/HTMLElement/Ext.Element} [centerIn] The element in which to center the element.
        */
        center : function(centerIn){
            return this.alignTo(centerIn || doc, 'c-c');
        }
    };
})());